Lithium ion secondary battery

Abstract

Provided is a lithium ion secondary battery capable of securing sufficient bonding area for bonding an insulating member capable of preventing short circuit of a positive electrode current collecting foil to the positive electrode current collecting foil. A lithium ion secondary battery 1 includes a laminate 10 in which a lithium-containing negative electrode 20 and a positive electrode 40 are laminated with an electrolyte 30 interposed therebetween, the positive electrode 40 including a positive electrode current collecting foil 41 and a positive electrode active material layer 42 laminated to the positive electrode current collecting foil 41, the positive electrode current collecting foil 41 including a positive electrode active material layer formation portion 410 which is a portion where the positive electrode active material layer 42 is formed, a current collecting foil exposed portion 411 which is adjacent to the positive electrode active material layer formation portion 410 and exposes a surface of the positive electrode current collecting foil 410, and a current collecting foil tab portion 412 which is disposed on the opposite side of the positive electrode active material layer formation portion 410 from the current collecting foil exposed portion 411 and is located at an end portion of the positive electrode current collecting foil 41, and an insulating member 60 is disposed so as to cover the surface of the current collecting foil exposed portion 411 and an end portion 415.

Description

Technical Field

[0001] This invention relates to a lithium-ion secondary battery. Background Technology

[0002] Previously, in lithium-ion secondary batteries, a technique was known to construct a laminate consisting of a lithium-containing negative electrode and a positive electrode comprising a positive electrode current collector foil and a positive electrode flux layer. Patent Document 1 is one example of a document describing this technique.

[0003] Patent Document 1 relates to a non-aqueous electrolyte secondary battery. In Patent Document 1, in the positive electrode plate of the non-aqueous electrolyte secondary battery, the current collector tab, the exposed portion of the metal foil, and the surface of the positive electrode active material layer adjacent to the exposed portion of the metal foil are covered with insulating tape. The insulating tape has a region where a slurry layer is formed and a region where it is not formed. Furthermore, the surface of the positive electrode active material layer is covered by the region of the insulating tape where the slurry layer is not formed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-055906 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, the heat generated during battery use can lead to malfunctions. For example, in lithium-ion secondary batteries with a separator between the positive and negative electrodes, when the temperature rises to around 150°C, the separator will thermally shrink. Damage or deformation of the separator may cause a short circuit between the positive and negative electrodes. Furthermore, when the temperature near the positive electrode current collector reaches around 180°C, molten lithium will flow and come into contact with the current collector, potentially causing a low-resistance short circuit.

[0009] By configuring insulating components, short circuits caused by diaphragm damage at high temperatures or external impacts can be prevented. However, the width of the current collector tab of the positive electrode current collector foil is narrower than the portion where the positive electrode active material layer is formed, making it difficult to ensure a large bonding surface on the current collector tab side of the insulating component. Therefore, the insulating component may peel off from the positive electrode current collector foil due to external impacts or contact with the diaphragm damaged by abnormal heating. There is room for improvement in the prior art regarding preventing the insulating component from peeling off.

[0010] The present invention aims to provide a lithium-ion secondary battery that can ensure sufficient bonding area for bonding insulating components that can prevent short circuits of the positive electrode current collector foil to the positive electrode current collector foil.

[0011] [Technical means to solve the problem]

[0012] (1) The present invention relates to a lithium-ion secondary battery (e.g., lithium-ion secondary battery 1 described later), comprising a laminate (e.g., laminate 10 described later) in which a lithium-containing negative electrode (e.g., negative electrode 20 described later) and a positive electrode (e.g., positive electrode 40 described later) are stacked with an electrolyte (e.g., electrolyte 30 described later) separated by an electrolyte (e.g., electrolyte 30 described later), wherein the positive electrode comprises a positive electrode current collector foil (e.g., positive electrode current collector foil 41 described later) and a positive electrode active material layer (e.g., positive electrode active material layer 42 described later) stacked on the aforementioned positive electrode current collector foil, wherein the aforementioned positive electrode current collector foil comprises: a positive electrode active material layer forming portion (e.g., positive electrode active material layer forming portion described later) The positive electrode active material layer forming portion 410 is the portion on which the aforementioned positive electrode active material layer is formed; the current collector foil exposed portion (e.g., current collector foil exposed portion 411 described later) is adjacent to the aforementioned positive electrode active material layer forming portion and exposes the surface of the aforementioned positive electrode current collector foil; and the current collector foil tab portion (e.g., current collector foil tab portion 412 described later) is disposed on the opposite side of the aforementioned positive electrode active material layer forming portion, sandwiching the aforementioned current collector foil exposed portion, and is located at the end of the aforementioned positive electrode current collector foil; and an insulating member (e.g., insulating member 60, 160 described later) is disposed to cover the surface and end of the aforementioned current collector foil exposed portion.

[0013] (2) The lithium-ion secondary battery according to (1) further includes a separator (e.g., separator 50 described later) disposed between the aforementioned negative electrode and the aforementioned positive electrode. In a predetermined direction in which the aforementioned current collector foil tab, the aforementioned current collector foil exposed portion, and the aforementioned positive electrode active material layer forming portion are arranged, with the aforementioned current collector foil tab side of the aforementioned positive electrode current collector foil as the outer side and the aforementioned positive electrode active material layer forming portion side as the inner side, the outer end of the aforementioned insulating member in the predetermined direction is configured to be located at a position further outward than the outer end of the aforementioned separator, and at a position further inward than the end of the aforementioned current collector foil tab on the side opposite to the aforementioned positive electrode active material layer forming portion.

[0014] (3) The lithium-ion secondary battery according to (1) further includes a separator (e.g., separator 50 described later) disposed between the aforementioned negative electrode and the aforementioned positive electrode. In a predetermined direction in which the aforementioned current collector tab, the aforementioned current collector exposed portion, and the aforementioned positive electrode active material layer forming portion are arranged, with the aforementioned current collector tab side of the aforementioned positive electrode current collector being the outer side and the aforementioned positive electrode active material layer forming portion side being the inner side, the aforementioned current collector exposed portion is disposed at a position further inward than the outer end of the aforementioned separator in the predetermined direction, and its width is equal to that of the aforementioned positive electrode active material layer forming portion.

[0015] (4) A lithium-ion secondary battery according to any one of (1) to (3), wherein the volume resistivity of the aforementioned insulating component is 1×10⁻⁶. 15 Ω·cm or higher.

[0016] (5) A lithium-ion secondary battery according to any one of (1) to (4), wherein the volume resistivity of the aforementioned insulating component is 1×10⁻⁶. 20 Below Ω·cm.

[0017] (6) The lithium-ion secondary battery according to any one of (1) to (5), wherein the thickness of the aforementioned insulating component is 5 μm or more and 100 μm or less.

[0018] (7) A lithium-ion secondary battery according to any one of (1) to (6), wherein the aforementioned positive electrode current collector foil is a composite current collector foil.

[0019] (8) The lithium-ion secondary battery according to any one of (1) to (7), wherein the aforementioned insulating component has heat-resistant adhesive properties.

[0020] (9) The lithium-ion secondary battery according to any one of (1) to (7), wherein the aforementioned insulating component has thermal fusion properties.

[0021] (10) A lithium-ion secondary battery according to any one of (1) to (9), wherein the battery further comprises a separator (e.g., separator 50 described later) disposed between the aforementioned negative electrode and the aforementioned positive electrode, and a conductive layer (e.g., conductive layer 51 described later) is formed on the aforementioned negative electrode side of the separator.

[0022] (The effect of the invention)

[0023] According to the present invention, a lithium-ion secondary battery can be provided that ensures sufficient bonding area for bonding an insulating component that can prevent short circuit of the positive electrode current collector foil to the positive electrode current collector foil. Attached Figure Description

[0024] Figure 1 This is a schematic cross-sectional view showing the configuration of a lithium-ion secondary battery according to one embodiment of the present invention.

[0025] Figure 2 This is an enlarged cross-sectional view showing the positional relationship between the positive electrode and the insulating component of the lithium-ion secondary battery according to this embodiment.

[0026] Figure 3 This is a perspective view showing the positional relationship between the positive electrode and the insulating component of the lithium-ion secondary battery according to this embodiment.

[0027] Figure 4 This is a perspective view showing the positional relationship between the positive electrode and the insulating component of a comparative example lithium-ion secondary battery.

[0028] Figure 5 This is a perspective view showing the positional relationship between the positive electrode and the insulating component of a modified lithium-ion secondary battery. Detailed Implementation

[0029] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic cross-sectional view showing the configuration of a lithium-ion secondary battery 1 according to one embodiment of the present invention. The lithium-ion secondary battery 1 of this embodiment includes a laminate 10. The laminate 10 includes a negative electrode 20, an electrolyte 30, a positive electrode 40, a separator 50, and an insulating component 60. In the following description, the stacking direction of each component of the laminate 10 is described as the stacking direction.

[0031] The positional relationship of each component of the laminate 10 is explained. In the components constituting the laminate 10, the negative electrode 20, the electrolyte 30, and the positive electrode 40 are arranged in the lamination direction in the order of negative electrode 20, electrolyte 30, and positive electrode 40. A diaphragm 50 is disposed between the negative electrode 20 and the positive electrode 40. An insulating member 60 is located between the diaphragms 50.

[0032] The negative electrode 20 is configured to contain lithium. The negative electrode 20 has a negative electrode active material layer 21 and a negative electrode current collector layer 22. The negative electrode active material layer 21 is formed on both sides of the negative electrode current collector layer 22 facing the stacking direction. In the stacking direction, the entire surface of the negative electrode active material layer 21 opposite to the negative electrode current collector layer 22 faces the conductive layer 51 of the separator 50, which will be described later.

[0033] The negative electrode active material layer 21 is not particularly limited and is composed of a known negative electrode active material used as a negative electrode active material layer. From the viewpoint of improving the energy density of the lithium-ion secondary battery 1, the negative electrode active material layer 21 is preferably a lithium metal layer in which the negative electrode active material is lithium metal. The aforementioned lithium metal includes lithium metal monomers and lithium alloys, etc. In addition to the above-mentioned materials, the negative electrode active material layer 21 may also be composed of silicon-based active materials such as Si and Si alloys, lithium titanate (Li4Ti5O4), etc. 12 It is composed of lithium transition metal oxides such as TiO2, Nb2O3 and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, and metal indium.

[0034] The negative electrode current collector layer 22 is not particularly limited and can be made of copper, nickel, or stainless steel. Examples of possible shapes for the negative electrode current collector layer 22 include foil, plate, mesh, non-woven fabric, and foam.

[0035] Electrolyte 30 is a lithium ion supply source that serves as a charge-movement medium and contains a lithium salt. Examples of lithium salts include LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(CF3SO2)2 (LiTFSI), LiN(FSO2)2 (LiFSI), and LiBC4O8. A single lithium salt may be used, or two or more may be used in combination.

[0036] Electrolyte 30 is present in the presence of an organic solvent as the electrolyte. Examples of organic solvents that can be used include cyclic carbonates, linear carbonates, cyclic ethers, linear ethers, hydrofluoroethers, aromatic ethers, sulfones, cyclic esters, linear carboxylic esters, and nitriles. One organic solvent may be used alone, or two or more may be used in combination.

[0037] Alternatively, a solid electrolyte can be used as electrolyte 30. In this case, electrolyte 30 is stacked between positive electrode 40 and negative electrode 20. As for solid electrolyte, it is not particularly limited as long as it has lithium-ion conductivity; for example, oxide-based electrolytes and sulfide-based electrolytes can be listed.

[0038] The positive electrode 40 includes a positive electrode current collector foil 41 and a positive electrode active material layer 42. The positive electrode active material layer 42 is formed on both sides of the positive electrode current collector foil 41 facing the stacking direction.

[0039] The material of the positive electrode current collector foil 41 is not particularly limited, and it can be made of a known current collector material used as the positive electrode current collector in a lithium-ion secondary battery. For example, the positive electrode current collector foil 41 can be made of a known composite current collector foil comprising a metal such as aluminum and a resin layer such as polyethylene, polypropylene, or polyethylene terephthalate. Furthermore, the positive electrode current collector foil 41 is not limited to a composite current collector foil, and can also be a single metal foil such as aluminum foil.

[0040] A positive electrode active material layer 42 is formed on the positive electrode current collector foil 41. In the positive electrode active material layer 42 of this embodiment, the side opposite to the side of the positive electrode current collector foil 41 in the stacking direction is opposite to the separator 50.

[0041] The positive electrode active material layer 42 contains the positive electrode active material, and may further contain conductive additives, binders, etc. As the positive electrode active material, it only needs to be able to absorb and release lithium ions; its material is not particularly limited, for example, lithium nickel cobalt manganese composite oxides. As the solid electrolyte, it only needs to have lithium-ion conductivity; there are no particular limitations, for example, oxide-based electrolytes and sulfide-based electrolytes. As the conductive additive, it only needs to have electronic conductivity; there are no particular limitations, for example, carbon black. As the binder, it only needs to improve adhesion; there are no particular limitations, for example, styrene-butadiene rubber.

[0042] The separator 50 may include a conductive layer 51. The conductive layer 51 is stacked on the separator 50. The conductive layer 51 is formed on the side of the separator 50 opposite to the positive electrode active material layer 43 (the negative electrode 20 side). The material of the conductive layer 51 is not particularly limited, and examples include carbon materials such as carbon black and carbon nanotubes, or materials containing metals such as copper.

[0043] The material of the diaphragm 50 is not particularly limited; for example, porous sheets or non-woven sheets can be used. Examples of porous sheet materials include polyethylene, polyolefins such as polypropylene, aramid, polyimide, and fluoropolymers. Examples of non-woven sheet materials include glass fiber and cellulose fiber.

[0044] Next, the insulating component 60 will be described. First, refer to... Figure 2 and Figure 3 This indicates the location of the insulating component 60. Figure 2 This is an enlarged cross-sectional view showing the positional relationship between the positive electrode 40 and the insulating component 60 of the lithium-ion secondary battery 1 of this embodiment. Figure 3 This is a perspective view showing the positional relationship between the positive electrode 40 and the insulating component 60 of the lithium-ion secondary battery 1 according to this embodiment.

[0045] First, the configuration of the positive electrode current collector foil 41, which is equipped with the insulating component 60, will be described. The positive electrode current collector foil 41 is formed into an elongated shape in a predetermined direction. Figure 2 and Figure 3 As shown, the positive electrode current collector foil 41 has three regions: a positive electrode active material layer forming portion 410, a current collector foil exposed portion 411, and a current collector foil tab portion 412. The positive electrode active material layer forming portion 410, the current collector foil exposed portion 411, and the current collector foil tab portion 412 are arranged along a predetermined direction of the positive electrode current collector foil 41. Figure 2 In this context, the side of the current collector foil tab 412 where the positive current collector foil 41 is formed, in a predetermined direction, is sometimes described as the outer side, and the other side where the positive active material layer forming portion 410 is formed, in a predetermined direction, is described as the inner side. Furthermore, the predetermined direction is not particularly limited, and in this embodiment, it is consistent with the length direction of the positive current collector foil 41.

[0046] The positive electrode active material layer forming portion 410 is the region where the positive electrode active material layer 42 is stacked, i.e., the positive electrode active material layer coating portion. Since the positive electrode active material layer 42 is stacked on the positive electrode active material layer forming portion 410, it is located on the back side of the positive electrode active material layer 42 when viewed in the stacking direction, and is therefore not visible from the outside. The positive electrode active material layer forming portion 410 is formed on both sides of the positive electrode current collector foil 41 facing the stacking direction.

[0047] The exposed portion 411 of the current collector foil is the region adjacent to the positive electrode active material layer forming portion 410, and is the part where the positive electrode active material layer 42 is not formed. Since the exposed portion 411 of the current collector foil is not stacked with the positive electrode active material layer 42, it is exposed to the outside when viewed in the stacking direction. The width of the exposed portion 411 of the current collector foil in the direction orthogonal to the predetermined direction (width direction) is equal to the width of the positive electrode active material layer forming portion 410 in the direction orthogonal to the predetermined direction (width direction), and the end faces of the exposed portion 411 of the current collector foil and the positive electrode active material layer forming portion 410 are continuous in the length direction. The exposed portion 411 of the current collector foil is formed on both sides of the positive electrode current collector foil 41 facing the stacking direction.

[0048] The current collector foil tab 412 is formed at one end of the positive electrode current collector foil 41 along its length, adjacent to the exposed current collector foil portion 411. The current collector foil tab 412 sandwiches the exposed current collector foil portion 411 and is located on the opposite side of the predetermined direction of the positive electrode active material layer forming portion 410. The width of the current collector foil tab 412 in the direction orthogonal to the predetermined direction is narrower than the width of the exposed current collector foil portion 411 and the width of the positive electrode active material layer forming portion 410 in the direction orthogonal to the predetermined direction, and it appears convex when viewed in the stacking direction. A joining portion 46, indicated by a dashed line, is formed in the current collector foil tab 412, through which a lead tab (not shown) is joined.

[0049] The insulating member 60 is configured to cover the entire surface area of ​​the exposed current collector foil portion 411. Furthermore, the insulating member 60 is provided with a length W1 in a predetermined direction, such that it, together with the exposed current collector foil portion 411, covers a portion of the inner side of the current collector foil tab portion 412 and a portion of the positive electrode active material layer forming portion 410. Moreover, the length W1 of the insulating member 60 in the predetermined direction is set so as not to overlap with the joint portion 46 formed on the outer side of the current collector foil tab portion 412.

[0050] Furthermore, the insulating member 60 covers at least a portion of the end 415 of the current collector foil tab 412 and the exposed current collector foil 411. The end 415 of the exposed current collector foil 411 is a portion that includes the end face (side face) of the exposed current collector foil 411 facing a direction orthogonal to a predetermined direction. The insulating member 60 may also be configured to cover not only the exposed current collector foil 411, but also a portion of the end face of the current collector foil tab 412 and the positive electrode active material layer forming portion 410.

[0051] Reference Figure 2 The dashed lines L0 to L5, indicated by the midpoint, illustrate the positional relationship of the positive electrode active material layer forming portion 410, the exposed current collector foil portion 411, the current collector foil tab portion 412, and the insulating member 60 in a specified direction. Furthermore, Figure 2The dashed line L0 indicates the position of the outer end of the current collector foil tab 412 in a predetermined direction. The dashed line L1 indicates the position of the outer end of the insulating member 60 in a predetermined direction. The dashed line L2 indicates the position of the outer end of the diaphragm 50 in a predetermined direction. The dashed line L3 indicates the position of the inner end of the current collector foil tab 412 in a predetermined direction, and also indicates the position of the outer end of the exposed current collector foil portion 411 in a predetermined direction. The dashed line L4 indicates the position of the outer end of the negative electrode 20 (negative electrode active material layer 21 and negative electrode current collector layer 22) in a predetermined direction. The dashed line L5 indicates the position of the inner end of the exposed current collector foil portion 411 in a predetermined direction, and also indicates the position of the outer end of the positive electrode active material layer forming portion 410 (positive electrode active material layer 42) in a predetermined direction. The dashed line L6 indicates the position of the inner end of the insulating member 60 in a predetermined direction.

[0052] As shown by dashed lines L0 and L1, the outer end of the insulating member 60 in a predetermined direction is located further inward than the outer end of the current collector foil tab 412. Furthermore, as shown by dashed lines L1 and L2, the outer end of the insulating member 60 in a predetermined direction is located further outward than the end of the diaphragm 50.

[0053] Furthermore, as shown by dashed lines L2 and L3, the outer end of the exposed portion 411 of the current collector foil in a predetermined direction is located further inward than the outer end of the diaphragm 50. Furthermore, as shown by dashed lines L3 and L4, the outer end of the exposed portion 411 of the current collector foil in a predetermined direction is located further outward than the outer end of the negative electrode 20.

[0054] Furthermore, as shown by dashed lines L4 and L5, the outer end of the positive electrode active material layer forming portion 410 in a predetermined direction is located further inward than the outer end of the negative electrode 20. Further, as shown by dashed lines L5 and L6, the inner end of the insulating member 60 in a predetermined direction is located further inward than the outer end of the positive electrode active material layer forming portion 410.

[0055] The physical properties of the insulating component 60 will be described. The insulating component 60 is formed as a thin film strip. From the viewpoint of effectively preventing short circuits in the positive electrode current collector foil, the thickness of the insulating component 60 is preferably 5 μm or more and 100 μm or less. The thickness of the insulating component 60 can be determined based on the thickness of the positive electrode active material layer 42. For example, the thickness of the insulating component 60 is preferably 5% or more and 30% or less of the sum of the thickness of the positive electrode active material layer 42 and the thickness of the separator 50, more preferably 10% or more and 20% or less. This suppresses the increase in the overall battery thickness caused by the thickness of the insulating component, and more effectively prevents short circuits in the positive electrode current collector foil. Furthermore, the volume resistivity of the insulating component 60 is preferably 1×10⁻⁶. 15For volumes above Ω·cm, there is no particular upper limit for volume resistivity; for example, it can be 1×10⁻⁶. 20 Below Ω·cm.

[0056] Furthermore, the insulating component 60 is made of a thin film of a resin with heat-welding properties. Examples of resins include polyethylene, polypropylene, polyethylene terephthalate, and polyimide; from the viewpoint of heat resistance, polyimide is preferred. The insulating component 60 has an adhesive surface and is bonded to the positive electrode current collector foil 41. The insulating component 60 can be made of Kapton (registered trademark) tape.

[0057] An example of a method for manufacturing a lithium-ion secondary battery 1 will be described. First, the following steps are performed: a positive electrode current collector foil 41 is configured, the positive electrode current collector foil 41 having a current collector foil exposure portion 411 extending with the same width as the portion where the positive electrode active material layer 42 is formed, i.e., the positive electrode active material layer forming portion 410, and a current collector foil tab portion 412 is formed adjacent to this current collector foil exposure portion 411. In the step of configuring the positive electrode current collector foil 41, the length (size) and configuration position of the positive electrode current collector foil 41 and the separator 50 are adjusted so that the outer end of the current collector foil exposure portion 411 in a predetermined direction is located further inward than the outer end of the separator 50.

[0058] Next, the following steps are performed: The insulating member 60 is disposed on both sides of the positive electrode current collector foil 41. In this step, the insulating member 60 is fixed to the positive electrode current collector foil 41 to cover the end faces of the exposed portion 411 of the current collector foil, the tab portion 412 of the current collector foil, and the positive electrode active material layer forming portion 410. In the configuration of disposing the insulating member 60 on the positive electrode current collector foil 41, the length (size) and placement position of the insulating member 60 are adjusted so that the outer end of the insulating member 60 in a predetermined direction protrudes further outward than the outer end of the separator 50.

[0059] By including these steps, a reference can be created. Figures 1-3 The description describes a lithium-ion secondary battery 1 that ensures the bonding area of ​​the insulating component 60.

[0060] Next, in order to explain the effect of the lithium-ion secondary battery 1 in this embodiment, refer to... Figure 4 Comparative examples will be described. Furthermore, the same reference numerals are used to denote components that are common to or the same as those in the embodiments described above, and detailed descriptions are omitted.

[0061] Figure 4 This is a perspective view showing the positional relationship between the positive electrode 240 and the insulating component 600 of a comparative example lithium-ion secondary battery. Figure 4As shown, the positive electrode 240 of the comparative example is composed of a positive electrode active material layer forming portion 241 and a current collector foil tab portion 242. Unlike the lithium-ion secondary battery 1 of the above embodiment, it does not have a current collector foil exposed portion 411. The positive electrode active material layer forming portion 241 and the current collector foil tab portion 242 are positioned adjacent to each other.

[0062] In the comparative example, the insulating member 600 is configured and bonded to cover a portion of the outer side of the positive active material layer 42 stacked on the positive active material layer forming portion 241 in a predetermined direction, and a portion of the inner side of the current collector foil tab portion 242. In the comparative example, the insulating member 600 can also be used to prevent short circuits between the current collector foil tab portion 242 and the negative electrode 20 side.

[0063] However, the width of the current collector foil tab 242 in the direction orthogonal to the predetermined direction is narrower than the width of the positive electrode active material layer forming portion 241. Therefore, the insulating member 600 of the comparative example cannot ensure sufficient bonding area of ​​the current collector foil tab 242 in the direction orthogonal to the predetermined direction, such as... Figure 4 As shown by the dotted line, the insulating component 600 is easily peeled off, which poses a risk that the insulating component 600 may peel off during battery use, causing a short circuit between the current collector tab 242 and the negative electrode 20.

[0064] Furthermore, since the insulating member 600 is bonded directly from the current collector foil tab 242 to the thick positive electrode active material layer 42, the end of the insulating member 600 faces upwards, creating a step on the surface of the positive electrode active material layer 42. The positive electrode 240 is composed of a separator 50, etc. Figure 4 The configuration not shown in the figure is constrained in the stacking direction, so pressure is not applied uniformly in the step sections. Due to the uneven application of pressure, lithium deposition tends to concentrate, forming an uneven deposition reaction, which leads to a reduced lifetime. In the configuration of the comparative example, uneven lithium deposition is prone to occur.

[0065] Regarding this, the lithium-ion secondary battery 1 of this embodiment is configured as follows. That is, the lithium-ion secondary battery 1 includes a laminate 10 in which a lithium-containing negative electrode 20 and a positive electrode 40 are stacked with an electrolyte 30 in between. The positive electrode 40 includes a positive electrode current collector foil 41 and a positive electrode active material layer 42 stacked on the positive electrode current collector foil 41. The positive electrode current collector foil 41 includes: a positive electrode active material layer forming portion 410, which is the portion where the positive electrode active material layer 42 is formed; a current collector foil exposed portion 411, which is adjacent to the positive electrode active material layer forming portion 410 and exposes the surface of the positive electrode current collector foil 41; and a current collector foil tab portion 412, which is disposed on the opposite side of the positive electrode active material layer forming portion 410 and sandwiches the current collector foil exposed portion 411, located at the end of the positive electrode current collector foil 41; and an insulating member 60 is disposed to cover the surface and end portion 415 of the current collector foil exposed portion 411.

[0066] Therefore, the exposed portion 411 of the current collector foil becomes a support for bonding the insulating component 60, ensuring a larger bonding area for the insulating component 60 compared to the configuration of the insulating component 600 in the comparative example. Furthermore, since the insulating component 60 is bonded from the current collector foil tab 412 across the exposed portion 411 to the positive electrode active material layer 42, the angle of the end of the insulating component 60 on the exposed portion 411 is gentler (relatively downward) compared to the comparative example, suppressing uneven lithium deposition caused by step differences on the positive electrode active material layer 42. Additionally, the portion of the positive electrode current collector foil 41 of the positive electrode 40 where the positive electrode active material layer 42 is not stacked, and its end 415, are covered by the insulating component 60, and the positive electrode current collector foil 41 is not exposed. Therefore, even if the separator 50 undergoes thermal shrinkage due to abnormal heating, short circuits between the exposed portion of the positive electrode current collector foil 41 and the negative electrode 20 can be prevented. In other words, both the function of preventing uneven lithium deposition and the function of preventing short circuits can be simultaneously achieved.

[0067] Furthermore, the lithium-ion secondary battery 1 of this embodiment also includes a separator 50 disposed between the negative electrode 20 and the positive electrode 40. In a predetermined direction (length direction) in which the current collector foil tab 412, the current collector foil exposed portion 411, and the positive electrode active material layer forming portion 410 are arranged, with the current collector foil tab 412 side of the positive electrode current collector foil 41 being the outer side and the positive electrode active material layer forming portion 410 side being the inner side, the outer end of the insulating member 60 in the predetermined direction is positioned further outward than the outer end of the separator 50, and further inward than the end of the current collector foil tab 412 on the side opposite to the positive electrode active material layer forming portion 410.

[0068] Therefore, while ensuring the engagement of the joint 46 on the current collector foil tab 412, the range of the insulating member 60 located further outward than the diaphragm 50 can be expanded, thereby more reliably preventing short circuits caused by thermal shrinkage or impact of the diaphragm 50 during abnormal heating.

[0069] Furthermore, the lithium-ion secondary battery 1 of this embodiment also includes a separator 50 disposed between the negative electrode 20 and the positive electrode 40. In a predetermined direction in which the current collector foil tab 412, the current collector foil exposed portion 411, and the positive electrode active material layer forming portion 410 are arranged, with the current collector foil tab 412 side of the positive electrode current collector foil 41 being the outer side and the positive electrode active material layer forming portion 410 side being the inner side, the current collector foil exposed portion 411 is disposed at a position further inward than the outer end of the separator 50 in the predetermined direction, and its width is equal to that of the positive electrode active material layer forming portion 410.

[0070] Sometimes, damage to the diaphragm 50 due to external impacts can cause damage to the insulating component 60, or the exposed portion 411 of the current collector foil may bend and puncture the insulating component 60 during current collection. In such cases, if the exposed portion 411 of the current collector foil protrudes outward from the diaphragm 50, a short circuit can easily occur between the negative electrode 20 or the conductive layer 51 of the diaphragm 50 and the exposed portion 411 of the current collector foil. In this regard, with the configuration of this embodiment, since the exposed portion 411 of the current collector foil is located further inward than the diaphragm 50, a short circuit at the exposed portion 411 of the current collector foil when the insulating component 60 is damaged can be avoided. Furthermore, since the width of the exposed portion 411 of the current collector foil is equal to the width of the positive electrode active material layer forming portion 410, a large bonding area of ​​the insulating component 60 can be ensured without complex processing. Furthermore, as in this embodiment, by positioning the outer end of the exposed portion 411 of the current collector foil further outward than the negative electrode 20, it is possible to suppress the occurrence of short circuits caused by damage to the insulating component 60 while maximizing the area to avoid adhesion.

[0071] Furthermore, the volume resistivity of the insulating component 60 in this embodiment can be 1×10⁻⁶. 15 The volume resistivity is above Ω·cm. Therefore, the insulating function of the insulating component 60 can be appropriately utilized. In this embodiment, the upper limit of the volume resistivity of the insulating component 60 is not particularly limited, and can be 1×10⁻⁶. 20 Below Ω·cm.

[0072] Furthermore, the thickness of the insulating component 60 in this embodiment can be 5 μm or more and 100 μm or less. Therefore, a lithium secondary battery with good insulation function can be achieved without adversely affecting the binding force due to the thickness of the insulating component 60. The thickness of the insulating component 60 is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and particularly preferably 5 μm or more and 30 μm or less.

[0073] Furthermore, the positive electrode current collector foil 41 in this embodiment can also be a composite current collector foil. By using a composite current collector foil containing resin, the resin in the positive electrode current collector foil 41 melts and cuts off the conductive path when abnormal heating occurs, thus more reliably preventing short circuits during abnormal heating.

[0074] Furthermore, the insulating component 60 in this embodiment can be constructed with heat-resistant adhesive properties. This prevents the adhesive from melting and causing the insulating component 60 to peel off from the positive electrode current collector foil 41 when heated.

[0075] Furthermore, the insulating component 60 in this embodiment can be configured to be heat-welded. Therefore, the insulating component 60 can be fixed to the positive electrode current collector foil 41 by heat fusion using methods such as hot pressing.

[0076] Furthermore, the lithium-ion secondary battery 1 of this embodiment also includes a separator 50 disposed between the negative electrode 20 and the positive electrode 40, and a conductive layer 51 is formed on the negative electrode 20 side of the separator 50. Therefore, by using both the insulating member 60 and the separator 50, short circuits caused by contact between the positive electrode 40 and the negative electrode 20 can be prevented more reliably. Furthermore, even if the separator 50 is damaged and a portion of the conductive layer 51 attempts to contact the exposed current collector foil 411, the insulating member 60 can prevent a short circuit from occurring.

[0077] Next, a variation of the lithium-ion secondary battery 1 according to the above embodiment will be described. In the following description, components that are the same as or identical to those described in the above embodiment will be marked with the same symbols, and detailed descriptions will be omitted.

[0078] Figure 5 This is a perspective view showing the positional relationship between the positive electrode 40 and the insulating member 160 of the modified lithium-ion secondary battery 1. In the following description of the modified example, it is assumed that the configuration other than the insulating member 160 is the same as that of the embodiment described above.

[0079] In this modified example, the length W2 of the insulating member 160 in the specified direction is set to be longer than the length W1 of the insulating member 60 in the specified direction described in the above embodiment. Therefore, the bonding area of ​​the current collector foil tab 412 of the insulating member 160 is larger than that in the above embodiment. Furthermore, the length W2 of the insulating member 160 in the specified direction is set to reach the vicinity of the joint 46. As described above, the insulating member 160 may also extend to the vicinity of the joint 46. Thus, insulation over a large area can be achieved using the insulating member 160, which has a longer length in the specified direction.

[0080] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and appropriate modifications can be made to the above embodiments within the scope of the spirit of the present invention. For example, in the above embodiments, the positive electrode active material layer forming portion 410, the current collector foil exposed portion 411, and the current collector foil tab portion 412 are arranged on both sides of the positive electrode current collector foil 41, and the insulating member 60 is respectively arranged on both sides, but it is not limited to this configuration. It is also possible to arrange the positive electrode active material layer forming portion 410, the current collector foil exposed portion 411, and the current collector foil tab portion 412 only on one side of the positive electrode current collector foil 41.

[0081] Figure Labels

[0082] 1. Lithium-ion secondary battery

[0083] 10-layer stack

[0084] 20 Negative electrode

[0085] 30 Electrolytes

[0086] 40 Positive electrode

[0087] 41 Positive current collector foil

[0088] 410 Positive electrode active material layer formation section

[0089] 411 Exposed part of current collector foil

[0090] 412 Current collector foil tab

[0091] 42 Positive electrode active material layer

[0092] 50 diaphragm

[0093] 60, 160 Insulating Components

Claims

1. A lithium-ion secondary battery, It comprises a stacked structure containing a lithium-containing negative electrode and a positive electrode separated by an electrolyte layer. The aforementioned positive electrode includes a positive electrode current collector foil and a positive electrode active material layer stacked on the aforementioned positive electrode current collector foil. The aforementioned positive electrode current collector foil includes: The positive electrode active material layer forming part is the part where the aforementioned positive electrode active material layer is formed; The exposed portion of the current collector foil is adjacent to the aforementioned positive electrode active material layer formation portion, exposing the surface of the aforementioned positive electrode current collector foil; and... The current collector foil tab is located on the opposite side of the positive electrode active material layer forming part, sandwiching the aforementioned exposed current collector foil portion, and is situated at the end of the aforementioned positive electrode current collector foil; An insulating component is provided to cover the surface and ends of the aforementioned exposed current collector foil.

2. The lithium-ion secondary battery according to claim 1, wherein, It also includes a separator disposed between the aforementioned negative electrode and the aforementioned positive electrode. In a predetermined direction in which the aforementioned current collector foil tab portion, the aforementioned current collector foil exposed portion, and the aforementioned positive electrode active material layer forming portion are arranged, with the aforementioned current collector foil tab portion side of the aforementioned positive electrode current collector foil being taken as the outer side and the aforementioned positive electrode active material layer forming portion side being taken as the inner side, the current collector foil tab portion side of the aforementioned positive electrode current collector foil being taken as the outer side is considered as the inner side. The outer end of the aforementioned insulating component in the aforementioned specified direction is configured as follows: It is located further outward than the outer end of the aforementioned diaphragm, and further inward than the end of the aforementioned current collector foil tab on the opposite side of the aforementioned positive electrode active material layer forming portion.

3. The lithium-ion secondary battery according to claim 1, wherein, It also includes a separator disposed between the aforementioned negative electrode and the aforementioned positive electrode. In a predetermined direction in which the aforementioned current collector foil tab portion, the aforementioned current collector foil exposed portion, and the aforementioned positive electrode active material layer forming portion are arranged, with the aforementioned current collector foil tab portion side of the aforementioned positive electrode current collector foil being taken as the outer side and the aforementioned positive electrode active material layer forming portion side being taken as the inner side, the current collector foil tab portion side of the aforementioned positive electrode current collector foil being taken as the outer side is considered as the inner side. The aforementioned exposed current collector foil is positioned further inward than the outer end of the aforementioned separator in the aforementioned predetermined direction, and its width is equal to that of the aforementioned positive electrode active material layer forming portion.

4. The lithium-ion secondary battery according to claim 1, wherein, The volume resistivity of the aforementioned insulating component is 1×10⁻⁶. 15 Ω·cm or higher.

5. The lithium-ion secondary battery according to claim 1, wherein, The volume resistivity of the aforementioned insulating component is 1×10⁻⁶. 20 Below Ω·cm.

6. The lithium-ion secondary battery according to claim 1, wherein, The thickness of the aforementioned insulating component is 5 μm or more and 100 μm or less.

7. The lithium-ion secondary battery according to claim 1, wherein, The aforementioned positive electrode current collector foil is a composite current collector foil.

8. The lithium-ion secondary battery according to any one of claims 1 to 7, wherein, The aforementioned insulating components have heat-resistant adhesive properties.

9. The lithium-ion secondary battery according to any one of claims 1 to 7, wherein, The aforementioned insulating components are heat-weldable.

10. The lithium-ion secondary battery according to any one of claims 1 to 7, wherein, It also includes a separator disposed between the aforementioned negative electrode and the aforementioned positive electrode. A conductive layer is formed on the negative electrode side of the aforementioned diaphragm.

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